In the development of chronic disease of the airways, there is a silent transition period. This proposal outlines an interdisciplinary approach to the study of this period and includes members from many departments of the Johns Hopkins Medical Institutions. Projects designed to define the etiology, risk factors and natural history of airways obstruction; projects designed to investigate acute reactions of the airways; and projects designed to study chronic reactions in the development of airways disease are included. The goal of these projects is to characterize the individual at risk in the development of chronic diseases of the airways. If successful, this program will provide indications for intervention and therapy in the process which leads toward irreversible disease.